The present invention relates to fluidically coupling fluidic components, in particular in a high performance liquid chromatography application.
In liquid chromatography, a fluidic sample (mobile phase) may be pumped through conduits and a column comprising a material (stationary phase) which is capable of separating different components of the fluidic analyte. Such a material, so-called beads which may comprise silica gel, may be filled into a column tube which may be connected to other elements (like a sampling unit, a flow cell, containers including sample and/or buffers) by conduits.
The flow path of the mobile phase typically comprises plural individual components coupled together, which, in turn, might also be comprised of individual sub-components. Due to the high pressure applied in most HPLC applications, pressure sealing of the components in and along the flow path is required. Sealings should also provide for a small dead volume and low carryover.
A so called fitting is a fluidic component being capable of providing a sealed connection between a capillary and another fluidic conduit (such as another capillary or a channel in a substrate or the like).
U.S. Pat. No. 4,991,883 discloses an apparatus for connecting first and second conduits having first and second bores, respectively, to provide communication between the first and second bores. The apparatus includes a base attached to the first conduit and a cap attached to the base. A follower is slidably disposed in the cap and is provided with a passageway, the second conduit extending through the passageway. A ferrule is received on the second conduit, the ferrule having a first end and a second end. The follower is biased against the first end of the ferrule. The first bore in the first conduit has a frustoconical surface which defines a receiving formation for the ferrule, the ferrule having a portion which is circular when viewed in transverse cross section. When the second end of the ferrule is urged in the receiving formation by the action of the biasing spring, the ferrule engages the frustoconical surface defining the receiving formation in substantially line contact.
U.S. Pat. No. 5,234,235 discloses an apparatus for connecting first and second conduits, which may be capillary columns, having first and second bores, respectively, to provide communication between the first and second bores for high temperature operation over wide variations in temperature. A monolithic fused quartz seating element is removably insertable into a seating chamber of a base that may be comprised of steel or other metal. The monolithic fused quartz seating element may be cylindrical and have frustoconical surfaces defining first and second receiving formations. First and second slidable followers biased by first and second quartz springs apply pressure against first and second ferrules to seal between the first and second receiving formations, and the first and second conduits, respectively.
U.S. Pat. No. 6,193,286 discloses a fitting which provides a means of making a union between a tube and a female fitting with low dead volume and without the use of tools. The fitting is comprised of a tube member that is pressed into the female fitting to automatically remove dead volume. The tube member is pressed into the fitting by a spring with the appropriate tension to hold the tube member against the expected pressure. The fitting also is comprised of a two piece nut assembly. The forward nut compresses a ferrule to create the high-pressure seal. The rearward nut is attached to the forward nut and provides compression and a holding means for the spring.
U.S. Pat. No. 6,494,500 discloses a universal self-adjusting high pressure liquid connector for use with high pressure liquid chromatography (HPLC) columns requiring liquid-tight and leak-free seals between fittings and unions. The apparatus provides a liquid-tight seal between the end of a HPLC end fitting and an end cap thereby eliminating any potential dead volume in the area of the connection. The apparatus comprises a body, a fixed ferrule, a replaceable ferrule, a stem disposed in the body and a biasing spring slidingly mounted on a capillary tube that extends through the connector. The spring biases the capillary tube of the connector into the HPLC end fitting, self-adjusting and maintaining a pressure sufficient to ensure a liquid-tight seal notwithstanding the depth of the HPLC tube stop or ferrule stop of the mating HPLC column.
However, the requirements regarding sealing performance and mechanical stability of a fluidic component of fluidic measurement devices increases with further increasing operation pressure values. At the same time, fast and easy handling of such a fitting by a user is required.